Field of the Invention
The present disclosure relates generally to insecticide formulations. The present disclosure relates more particularly to aqueous pymetrozine formulations that can be provided in concentrate form and methods for making them.
Technical Background
Pymetrozine is an azomethine insecticide commonly used in integrated crop management to control aphids, whiteflies and other pests. It is plant-systemic and readily taken up by leaves and roots and translocated throughout the plant. Plants are immediately protected upon application because insect feeding stops soon after ingestion of pymetrozine. While pymetrozine is generally considered safe for use on food crops, there is evidence of carcinogenic effects at high doses.
The conventional formulation of pymetrozine is as a so-called “wettable powder,” in which the pymetrozine is provided in a finely ground state combined with wetting agents and sometimes bulking agents. For application to plants, the wettable powder is dispersed in a large quantity of water and sprayed over a field. Wettable powders can be advantageous in that the pymetrozine can be provided in concentrated form and thus the weight and volume of a dilute pymetrozine suspension need not be managed until the point of use. However, wettable powders have a serious disadvantage: they can be rather dusty, and can create dust pollution and an acute inhalation hazard to operators (especially problematic given the potential carcinogenicity of pymetrozine).
Water-based formulations are considered much more environmentally benign and safe, as they produce no dust and include little or no aromatic solvent. Microparticulate pymetrozine can be suspended in water at relatively high concentrations to produce a suspension concentrate. Suspension concentrates can overcome the problems with dust of wettable powders, and can provide a number of additional advantages, such as ease of pouring and measuring. However, it can be difficult to prepare suspension concentrate formulations that are storage stable, e.g., with respect to thickening and particle agglomeration, especially for active ingredients having high water solubility such as pymetrozine.
There remains a need for pymetrozine formulations that can address these shortcomings.